Confusing error message when mis-spelling macro invocation

[jethrogb]

When compiling

thread_local {
    static I: i32 = 0;
}

the following error is generated

error: expected one of `!` or `::`, found `{`
 --> m.rs:1:14
  |
1 | thread_local {
  |              ^

This happens because the only thing that could possibly be in an item position and not start with a keyword is a macro, and macros start with a path. A path can contain double colons. However, a macro invocation can not, and the compiler will generate an error at a later stage if you try to invoke a macro that way. See #28558

To be clear, I think the error message should just be “expected `!`, found `{`”.

[petrochenkov]

A path can contain double colons. However, a macro invocation can not

This will change pretty soon - #38082

[jethrogb]

I suppose it's not feasible to change the parser error message based on whether the feature is activated?

[jseyfried]

@jethrogb It's feasible, but I don't think the extra complexity is worth it.

[jethrogb]

Closing this because macros 2.0 is pretty much around the corner.